The invention is based on a fuel injection pump for an internal combustion engine. In an injection pump of this type, known from German Pat. No. 915 163, the injection pump is embodied as a so-called pump/nozzle, having a pump piston the end face of which defines a pump work chamber and controls the inflow bore through which the pump work chamber is filled. An oblique control groove is furthermore provided on the jacket face of the pump piston and cooperates with a groove communicating with the pump work chamber; when the control groove and this latter groove coincide during the compression stroke of the pump piston, the remainder of the pumped fuel is permitted to flow out to an overflow reservoir, and at the same time the pumping of fuel out of the pump work chamber to an injection location is interrupted. The overflow chamber is uncoupled from the fuel supply source by a check valve. By means of the rotation of the pump piston, the work chamber is opened up earlier or later during the compression stroke of the pump piston, thus determining the quantity of fuel actually injected. The fuel flowing out during the remainder of the compression stroke is stored, and it then becomes the first fuel returned to the work chamber at the beginning of the intake stroke of the pump piston. The onset of injection of this injection pump is determined by the closure of the inflow bore to the work chamber, that is, by the onset of the compression stroke of the pump piston. The adjustment of the injection onset is effected by influencing the drive means of the pump piston.
In this fuel injection pump, by means of which only a single injection location can be supplied with fuel, the reservoir must be capable of receiving a variable quantity of fuel, because of the difference between the maximum and the minimum injection quantity. The reservoir must accordingly be relatively large. Furthermore, complicated mechanical means are required for adjusting both the instant of injection and the injection quantity. In this embodiment, the supply stroke disadvantageously always occurs at the same point on the cam elevation curve, so that the injection characteristic cannot be intentionally changed but instead varies unintentionally and disadvantageously depending upon the injection quantity.